Guy Davis - Software Programmer/Developer

Google releases App Inventor framework

Mon, 12 Jul 2010 18:51:26 GMT

Today, Google released App Inventor, an interesting software development framework for the Android smartphone OS. They are pushing it as a means of building an application without needed any knowledge of a programming language. This is a great idea that will hopefully open up the phone to more applications. Granted, most of these applications will be simple ones, but an app doesn't have to be professional to be useful.

App Inventor is builds on the same foundations as the similar Scratch visual programming language which uses drag and drop of visual blocks to replace the need to code in a textual programming language. I recently had good success using Scratch to introduce a Metis youth to programming during a job shadowing exercise. I'm excited to see this accessible form of programming on a key computing platform, the smartphone.

Unfortunately, I won't be participating with my own Android phone anytime soon. After years of waiting for cheaper data plans in Canada, the battery on my 5 year old LG flip-phone finally died. Since I refuse to get a smartphone (either iPhone or Android unit) until phone plans become less expensive in Canada, I opted instead to get a pay-as-you-go phone from 7-11. For probably $5-$10 a month, I get voice calling, voicemail, and free incoming texts. Maybe one day, I'll actually get an Android phone and try out some of the cool applications being built. I'm not holding my breath that Canadians will get a break on our mobile phone plans any time soon though.

Why Geo-Exchange Heating?

Mon, 21 Jun 2010 18:52:21 GMT

To provide the heat for the radiant in-floor system, we could have used either a natural gas boiler or a ground-source heat pump (GSHP). We decided on geo-exchange (via the GSHP) as a year-round, constant source of renewable energy. A local installer, Thermal Creek, is installing the Nordic heat-pump which is made in New Brunswick.

Low Carbon Footprint

Geo-exchange can potentially be carbon-emissions free, depending on the source of the electrical power driving the pump. For the first few years we'll be drawing power from the Alberta grid which means dirty coal-powered electricity. So initially, our carbon footprint will not be much improved over natural gas. However, we plan to add solar photovoltaic panels within 5 years, providing carbon-free electricity to run the GSHP. At that point, the house will approach Net Zero.

Efficient Heating

The beauty of geo-exchange is that you only provide electrical energy to drive the pumps. The natural year-round warmth of the earth provides the heating for your home. This can lead to incredible efficiencies of between 300% to 500%. Compare that to a high-efficiency natural gas furnace running around 90% efficient and you start to see the benefits of geo-exchange.

Payback Period

Due to the high initial cost of the drilling and heat-pump required for geo-exchange, the payback period is measured in decades. Even factoring in the $10K Alberta New Home grant, geo-exchange still has a steep initial cost. In our case, the high cost of a natural gas boiler meant the price difference was close enough to justify spending more for a renewable energy source.

Read more about our new home project...

Why Solar Hot Water?

Mon, 21 Jun 2010 18:51:08 GMT

Alison and I decided to spend on renewable energy for our new home. After evaluating the choices, an evacuated-tube solar hot water heating system rose to the top of the list. We went with a local company, Simple Solar, to handle the installation.

Mature, Efficient Technology

Unlike solar photovoltaic panels which generate electricity at about 20% efficiency, evacuated-tube solar collectors operate at 80% efficiency or better. Basically, heating water efficiently with the sun is a solved problem with little room for improvements. On the other hand, generating electricity with solar panels clearly has lots of room for improvement. So we'll be holding off on solar photovoltatic panels for 5 years, hoping for a breakthrough in price and efficiency.

Best Payback Period

Renewable energy alternatives are often compared to fossil fuel energy solely on cost to buy and cost to run. In Alberta, that is a very challenging comparison given the currently low cost of natural gas. On such a pure payback comparison using today's fossil fuel prices, renewable energy sources such as solar thermal have payback periods extending over decades.

Factoring in the $10K Alberta government grant for a 86+ Energuide house, makes the payback quite reasonable. Then assume some reasonable price increases in natural gas over the coming years and solar thermal panels make a lot of financial sense.

Carbon Footprint

Since Simple Solar's panels include a small photo-voltaic panel to generate electrical power for the pump, the solar collector is completely carbon-emission free. We'll still be drawing a bit of natural gas for final "top-up" heating, but overall our domestic hot water heating needs will use a small fraction the natural gas of a regular house.

Read more about our new home project...

Why build Green?

Mon, 21 Jun 2010 18:49:13 GMT

What does it mean to "build a Green home"? Green is a very overloaded term these days. I've seen it applied to everything from a straw-bale house up to a 10,000 sq. ft. mansion. In designing our average-sized new home, we had to decide on our environmental priorities and make trade-offs. We settled upon a house that was:

Very energy efficient.
Had a low carbon footprint.
Had great indoor air quality.

After a bit of initial research, I realized our best choice was a very tight and well insulated home. We would have active fresh air circulation using a heat-recovery ventilator (HRV). This approach let us maximize the energy efficiency of the house while still having a healthy home.

Air Tightness

In terms of air sealing, we are aiming for less than one air change per hour during a blower door test. That is less than a third of a normal new home. Less hot air leaking out of the house, means lower heating bills and a more energy efficient home. Our builder, Avalon, has demonstrated experience in building very tight homes.

Insulation

For the exterior walls, we faced a tough choice between polyurethane structural insulated panels (SIPs) or polyurethane spray foam with 2x6 lumber construction. Both offered comparable insulating value for a similar price (in our case). In the end, we went with the SIPs which should offer less thermal bridging.

Heating

In our climate, most energy is devoted to heating and domestic hot water (DHW). Once we decided on radiant in-floor heating for comfort, we found that there were efficiencies and savings to relying on hot water for both uses. We are installing a pair of solar thermal panels on the roof which will provide the bulk of our DHW use. The ground-source heat pump (GHSP) will meet the heating needs of the house and provide extra DHW heat using the constant warmth of the earth.

My wife and I both feel that fossil-fuel dependency is untenable and renewable energy solutions are the solution in the long term. For more on our renewable energy choices, please read "Why Solar Hot Water?" and "Why Geo-Exchange Heating?".

Choosing Change

At the end of the day, this house will cost a lot of money. If the balance sheet was the only thing we cared about, we would be renting on the outskirts of Calgary. However, Alison and I both felt that we wanted a really great home that would meet the needs of our family for many decades. We are voting with our dollars here; saying yes to energy efficiency and renewable energy.

Our hope is that we are helping to make these technologies cheaper, so that more families can benefit from them in the future. Some people take vacations around the world, some buy fancy cars, and some have all the latest electronic gadgets. In our case, we'd rather have a very efficient home which will hopefully point the way towards a more sustainable future.

Read more about our new home project...

Basement development

Fri, 11 Jun 2010 03:18:21 GMT

The basement slab has been poured and work begun on the basement suite in earnest. With a lot of muscle, the builders' crew was able to maneuver the 800lb ground-source heat-pump into the mechanical room, ready for hookup. Overall I'm happy with the progress, but I've been a bit dismayed by a few mistakes that have taken time to correct or even meant we've deviated from the plans. Hopefully, things will go more smoothly over the summer.

Read more about our new home project...

Welcoming Connor Davis

Fri, 14 May 2010 17:37:18 GMT

Alison gave birth to our 2nd son, Connor Kent Davis, in the early-afternoon yesterday (May 13th). He weighed in at a hefty 9lbs 13oz (4448 grams) and was 22 inches long (56 cm). He arrived only a day before his due date and is doing great. He took to breast-feeding right away and has passed all his Dr's check-ups with flying colors. Alison had an outstanding 8 hour labor and is recovering nicely now. Gavin has met Connor and has promised to be a great big brother.

Ali and I really like the name Connor which means 'strong-willed' and felt it was reasonably common without being too popular. Following the practice we started with Gavin, we chose a middle name to honor a maternal great-grandfather. For Gavin's middle name, Thomas was Alison's grandfather from Scotland. In this case, Kent was the middle name of my grandfather. His first name was actually Guy, but we felt naming our son Guy in his honor wasn't a great idea.

Thanks to everybody for their congratulations. We'll be resting up for a little while, but look forward to visiting with you all soon and introducing you to Connor. Friends and family can view more photos. (requires login)

Mechanical systems and siding progressing

Thu, 22 Apr 2010 01:34:06 GMT

For the last couple of months, the tradesmen have been installing the plumbing, electrical, HRV ducting, and network cables. On the exterior of the house, the shingles have gone on the roof and the Hardie board siding is being installed. I just took a series of photos of the basement with drains shown, before the basement slab is poured. You never know when you'll need the location of drains under the slab. Actually, hopefully never...

Read more about our new home project...

Feds shut down housing efficiency program

Sun, 04 Apr 2010 19:11:18 GMT

Proving that all good things come to an end, the Federal government quietly and abruptly shutdown the EcoEnergy retrofit program. The program offered rebates on purchases of energy efficient improvements to existing homes. For example, some of the green tech we're adding to our house had the following rebates:

Geo-exchange system for heating and cooling: $4375
Solar hot-water collector on the roof: $1250
Drain-water heat recovery unit: $125

The program was so successful it was costing the Feds more than they could afford. Somehow they still have millions of dollars to give to single company for the wishful thinking known as 'Carbon Capture and Storage" though.

Since we are building a new home, we were excluded from the program as it was only for existing homes. So I definitely would have liked to see the rebate program extended to new homes as it has been in the US. However our politicians would rather kill a good idea so they can keep funding stupid ones for big industry. Sounds "Conservative" to me...

House now fully framed

Thu, 25 Feb 2010 02:26:30 GMT

Progress on our house is going well. The builder has now completed the framing stage, including all windows and doors. The plumber has even started laying the PEX tubing into the Warmboard radiant-heated sub-floor. Now they'll turn their attention to the electrical, plumbing, and other mechanical systems.

Read more about our new home project...

Release Planning based on Team Velocity

Sun, 21 Feb 2010 20:52:04 GMT

Due to a recent shake-up at work, I've been asked to handle release planning for our software product. Up to now, I've been primarily concerned with iteration planning for our two-week sprints. Release planning covers a wider scope of up to a year in our case. So I was handed a MS Excel spreadsheet which held the release plan from our previous manager. I was a bit surprised by what I found.

First some history. Our team follows a Scrum process using the XPlanner web app for tracking (shown on right). We've done this for a number of years now and it has worked well for us. Key steps in this process for us:

Entire team estimates using planning poker. This gives better task estimates which the team feels committed to achieving.
We learn from our successes and failures by holding sprint retrospectives. This helps improve our estimates going forward.
We use our project velocity to guide our workload for the next iteration.

Considering our commitment to Agile software development, I was surprised to see the release plan spreadsheet consisted of:

New features (user stories) estimated by the manager in terms of days of effort required.
A static resource analysis that assumes project velocity is simply number of hours in the office, discounted by a factor of 0.7.
Finally, the spreadsheet didn't actually prioritize every story in a single list. It just grouped them into quarters, within which no priority was given.

This traditional analysis is flawed in a few key ways:

Since the team didn't have input on the story estimates, they feel they don't have control over the process and are not committed to the goal of accomplishing the work in the estimated time.
By planning release milestones using a theoretical resource calculation, the release plan ignores a key team metric: project velocity. Project velocity is the number of story points completed in an iteration. When normalized to 100% team strength, this velocity number can be used to predict how many prioritized stories can be completed in the coming sprints.

Since a key function of the product backlog is to provide a total ordering of the stories by priority, I've moved the product backlog out of the spreadsheet and into XPlanner. We're now using our project velocity to determine which stories will be completed in which milestone. Finally, I've started getting story estimates from the entire team.

Should upper management still require burn up charts in spreadsheets for reporting, I'll generate them periodically from XPlanner. Hopefully, this more realistic approach will begin to improve our release process, resulting in better software releases in the future.

Note: We're currently estimating both the sprint backlog and product backlog in ideal time. I'd like to adopt Mike Cohn's approach of using different units (story points) for the product backlog soon.